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SINGAPORE – Questions have been raised following reports of three cases of anaphylaxis, or the rapid onset of severe allergic reactions, following the Covid-19 vaccination in Singapore.
The Straits Times looks at the severity of these reactions and whether they should be cause for concern.
Q: Why can the Pfizer-BioNTech vaccine cause anaphylaxis in people, even if they don’t have a history of it?
A: Professor Dale Fisher, a senior infectious disease consultant at the National University Hospital, said a possible reason could be that the vaccine contains polyethylene glycol (PEG), which is an adjuvant, or an ingredient used to create a stronger immune response. . He added that the chemical is used in some medications and has caused anaphylaxis in the past, although cases have been rare.
Infectious disease expert Leong Hoe Nam of Mount Elizabeth Novena Hospital said another possibility could be allergic reactions to lipid nanoparticles, which are used to stabilize the mRNA in the vaccine so that the body doesn’t destroy it too quickly.
Dr. Asok Kurup, who chairs the Infectious Disease Physicians Chapter of the Academy of Medicine, said there is a possibility that such reactions are unpredictable.
He added that all medical professionals have been advised to ensure that all post-vaccination observation sites have “the relevant support and supplies to treat anaphylaxis and other serious reactions.” Some patients who have had previous severe reactions that do not amount to anaphylaxis may also choose to be vaccinated in hospitals.
Q: What are the general causes of anaphylaxis?
A: Dr. Tseng Hsien-Cho, a lead physician for the Raffles Medical Group, who is also involved in the vaccination center’s operations, said that anaphylaxis is the result of an overreaction of the natural immune system to a trigger.
This could be something one is allergic to, but it might not always be the case, he noted.
Common triggers include foods such as nuts, milk, fish, shellfish, or eggs, as well as medications such as antibiotics or non-steroidal anti-inflammatory drugs and insect bites.
However, there may be cases where there is no obvious trigger, which is known as idiopathic anaphylaxis, Dr. Tseng said. This explains why those who have received the vaccine are observed for 30 minutes afterwards as a precaution.
Professor Paul Tambyah, President of the Asia Pacific Society for Clinical Microbiology, said that seafood and non-steroidal anti-inflammatory drugs, such as ibuprofen, are the most common causes of anaphylaxis in adults and children in Singapore.
Symptoms of anaphylaxis are usually severe and almost immediate, Professor Fisher said. These include swelling of the face and airways, wheezing, and a drop in blood pressure.
Q: How can anaphylaxis be treated?
A: An adrenaline auto-injector, or an Epipen, can be used to quickly reverse allergic reactions, for example by improving breathing and reducing swelling, Dr. Tseng said. A second injection may be given after five to 15 minutes if symptoms do not improve.
Other treatment options include an oxygen mask to help with breathing, fluids that are injected directly into a vein to increase blood pressure, as well as other medications such as antihistamines and steroids to relieve symptoms.
Q: Is anaphylaxis also a common reaction to other types of vaccines?
A: Allergic reactions are a common risk for all vaccines, and allergies may or may not be known to the patient and the physician, Dr. Tseng said.
Professor Fisher said that anaphylaxis is a rare side effect that affects one or two people for every million vaccines. The effect has also been described in influenza vaccines, pneumococcal vaccine, hepatitis A vaccine, and MMR vaccine (which prevents measles, mumps, and rubella).
Flu vaccines are known to cause anaphylaxis in people with severe allergies to eggs, as many flu vaccines are made using egg-based technology, said Professor Tambyah.
Q: Should I keep taking the vaccine if I have any known allergies?
A: Yes, although it is recommended that you discuss this with your doctor if you are concerned.
Before receiving the vaccine, people will be asked to share their medical history and complete a health assessment form to report any known allergies, Dr. Tseng said.
“Doctors will have to weigh the risk and benefit of vaccination. For example, if a person has known allergic reactions, such as small patches of rashes that can be treated with antihistamines, the benefits of receiving a vaccine would outweigh the risk.” he said.
However, Dr. Leong Choon Kit, a family physician at Mission Medical Clinic, whose clinic is one of 21 public health preparedness clinics that have begun administering the vaccines, said that people with previous allergies, such as allergic rhinitis, have the same chance of developing anaphylaxis as others, and do not face a significantly higher risk.
Professor Tambyah said that people with a history of “severe food or drug allergies” should consult their doctors beforehand, although this does not apply to people with allergic rhinitis or eczema, as the mechanisms of these conditions are slightly different
Q: When do I need to see a doctor for symptoms or side effects of the vaccine?
A: According to the Ministry of Health website, most side effects, including pain, redness, swelling at the injection site, fever, chills, headache, and muscle and joint pain, generally resolve on their own in three days. To alleviate these symptoms, one to two acetaminophen tablets can be taken every six hours when needed.
Although rare, it is also possible to experience swollen lymph nodes after receiving the vaccine. This usually takes seven to ten days to resolve.
However, you should see a doctor if your symptoms persist or worsen, or if the fever persists for more than two days.
If you experience a severe allergic reaction, such as difficulty breathing, swelling of the face, throat, eyes, or lips, dizziness and weakness, or a severe rash all over the body, seek medical attention immediately.
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